The invention generally concerns the packaging of food, particularly meat. The invention was made during attempts to make improved functional xe2x80x9cfreezer bagsxe2x80x9d for repackaging and freezer storing uncooked red meat by the ultimate consumer in a manner that reduces so called xe2x80x9cfreezer burnxe2x80x9d. Other aspects of the invention include methods for preparing the freezer bags and materials and methods for using the bags, for example.
Reclosable plastic storage bags are relatively old in the art. Today, plastic bags are typically available to the public in cartons identified for specific recommended xe2x80x9cend usexe2x80x9d (such as Storage Bags, Heavy Duty Freezer Bags, Vegetable Bags, Trash Bags). Often the bag itself is labeled by xe2x80x9cend usexe2x80x9d, e.g., xe2x80x9cZIPLOC(copyright) BRAND Heavy Duty Freezer Bagsxe2x80x9d.
The term xe2x80x9cfreezer bagxe2x80x9d is hereby defined as a bag having significant functional utility in the storage of food in a freezer. xe2x80x9cFreezer Bagsxe2x80x9d are typically available in the following sizes: 2 gallon; 1 gallon; pleated xc2xd gallon; quart; and pint.
The term xe2x80x9cfreezer burnxe2x80x9d is hereby defined as the name for the dehydration that occurs when unpackaged or improperly packaged food is stored in the low humidity atmosphere of a freezer (see xe2x80x9cPackaging Foods With Plasticsxe2x80x9d, by Wilmer A. Jenkins and James P. Harrington, published in 1991 by Technomic Publishing Co., In., at page 305). Consumers typically describe freezer burn in terms of three main visual attributes: ice crystal formation, product dehydration and color change.
Freezer burn has remained a major complaint among consumers despite the commercial success of thick plastic freezer bags. In the short term, freezer burn can be a reversible process. In the long term, however, freezer burn causes a complex deterioration of food quality involving undesirable texture changes followed by chemical changes such as degradation of pigments and oxidative rancidity of lipids. Taste, aroma, mouth feel and color can all be ruined. Freezer burn of raw red meat is particularly critical because of its impact upon the color of the meat.
Aforementioned xe2x80x9cPackaging Foods With Plasticsxe2x80x9d provides an excellent state of the art summary, with information on (commercial) packaging fresh red meat collected in chapter seven. Curiously, the book does not appear to mention freezer burn, apart from defining it in the glossary.
Additional reference information is provided in xe2x80x9cKeeping Food Freshxe2x80x9d, an article in xe2x80x9cConsumer Reportsxe2x80x9d for March 1994, at pages 143-147. The article contains a general overview of food storage products. More particularly, the article attempts to answer questions as to which packaging material (plastic, aluminum, waxed paper, bags, wraps or reusable containers) do the best job of (1) keeping food fresh for xe2x80x9cthe long haulxe2x80x9d, (2) at lowest overall cost, and (3) with minimum adverse environmental impact. It xe2x80x9ctop ratesxe2x80x9d ZIPLOC(copyright) Pleated Freezer Bags (at page 145). It points out that food stored in plastic containers can suffer from freezer burn if the container contains too much air. Concerning xe2x80x9cwrapsxe2x80x9d (plastic films and freezer papers), interestingly it advised against double wrapping because of cost and environmental reasons and it was noted that tests showed that double wrapping doesn""t afford much extra protection anyway.
The patent literature contains descriptions of various types of bags having liners or double walls including some space between the walls. Some of these patents relate to the transportation and storage of food. U.S. Pat. No. 4,211,091 (Campbell) concerns an xe2x80x9cInsulated Lunch Bagxe2x80x9d. U.S. Pat. No. 4,211,267 (Skovgaard) describes a xe2x80x9cCarrying Bagxe2x80x9d for xe2x80x9cgetting home with frozen food before it thawsxe2x80x9d. U.S. Pat. No. 4,797,010 (assigned to Nabisco Brands) discloses a duplex paper bag as a xe2x80x9creheatable, resealable package for fired foodxe2x80x9d. U.S. Pat. No. 4,358,466 (assigned to The Dow Chemical Company) relates to an improved xe2x80x9cFreezer to Microwave Oven Bagxe2x80x9d. The bag is formed of two wing shaped pouches on each side of an upright spout. U.S. Pat. No. 5,005,679 (Hjelle) concerns xe2x80x9cTote Bags Equipped With A Cooling Chamberxe2x80x9d. All of these food bags appear to have very thick food contacting walls compared to the invention described hereinafter. None of these patents appear to focus on freezer burn.
A more recent development in the art is disclosed in U.S. Pat. No. 5,804,265 which is assigned to S.C. Johnson Home Storage, Inc. This patent discloses an unique bag within a bag design specifically intended, although not limited in use, to controlling freezer burn. While tests show that this bag within a bag embodiment is clearly an advancement over other known storage bags, improvements in terms of product efficiency and material cost savings, among others, are desirable.
In its broadest scope, the present invention provides a freezer bag comprising a multi-layered bag including an outer support bag and an inner liner. The outer support bag includes two sidewalls attached together along respective lateral edges forming edge seals, said sidewalls having top edges which define an opening to the multi-layered bag and a folded edge defining the bottom of the multi-layered bag. The inner liner generally includes at least one sidewall which is attached along at least one edge to an inner surface of the respective sidewall of the outer support bag. The inner liner also includes at least one free or discontinuous edge as opposed to all closed edges which gives rise to an inner bag.
The present invention further relates to a process for making multi-layered bags having an outer support bag and at least one inner liner comprising the steps of forwarding a first thermoplastic film having a first thickness and a first transverse web width, forwarding a second thermoplastic film including two separate sheets having a second total thickness and a second total transverse web width, the second transverse web width being smaller than the width of the first thermoplastic film, overlaying the second thermoplastic film onto the first thermoplastic film between the edges of the first film, attaching the second thermoplastic film to the first thermoplastic film, folding the films in the transverse direction and seal cutting the folded films to form a multi-layered bag.
The present invention also relates to a process for making multi-layered bags having an outer support bag and at least one inner liner comprising the steps of forwarding a first thermoplastic film having a first thickness and a first transverse web width, forwarding a second thermoplastic film including two separate sheets, the second film preferably having a second thickness and a second transverse web width which is smaller than the width of the first thermoplastic film, perforating or slitting the second thermoplastic film, overlaying the second thermoplastic film onto the first thermoplastic film between the edges of the first film, attaching the second thermoplastic film to the first thermoplastic film, folding the films in the transverse direction and seal cutting the folded films to form a multi-layered bag.
Another process in accordance with the teachings of the present invention relates to heat sealing at least two film webs comprising the steps of providing at least first and second film including at least one sheet, the webs capable of being heat sealed together, perforating or slitting the second thermoplastic film, overlaying the second film web onto the first film web, providing at least one sealing band of material having a temperature, mass and heat capacity sufficient to heat seal the second thermoplastic film to the first thermoplastic film and applying the band of sealing material to the overlaid film webs. Preferably, the band seal is compressed between rollers after having been applied.
Yet another process in accordance with the present invention relates to heat sealing at least two film webs comprising the steps of providing at least a first film and a second film including multiple sheets, said webs capable of being heat sealed together, perforating or slitting the second thermoplastic film, overlaying the multiple sheets of the second film web onto the first film web, providing at least one sealing band of material having a temperature, mass and heat capacity sufficient to heat seal the second thermoplastic film to the first thermoplastic film and applying the band of sealing material to the overlaid film webs. Preferably, the band seal is compressed between rollers after having been applied.
Further according to the present invention, there is a process for attaching at least two film webs comprising the steps of providing at least first and second film webs having first and second widths respectively, perforating or slitting the second film web, overlaying the second film web onto the first film web between parallel edges of the first film web, providing at least one sealing band of material capable of being heat sealed to at least a portion of both film webs and applying the sealing band of material along and over parallel edges of the second film web.
Still another process according to the teachings of the present invention relates to a process for attaching at least two film webs comprising the steps of providing at least a first film web having a first web width and a second film including multiple sheets wherein the total of the multiple sheets gives a second web width, perforating or slitting the second film web, overlaying the multiple sheets of the second film web onto the first film web between parallel edges of the first film web, providing at least one sealing band of material capable of being heat sealed to at least a portion of both film webs and applying said sealing band of material along and over parallel edges of the second film web.
Further according to the present invention is an apparatus for making multi-layered bags having an outer support bag and at least an inner liner comprising means for forwarding a first thermoplastic film web having a first thickness and a first transverse web width between parallel edges, means for forwarding a second thermoplastic film web having a second thickness and a second transverse web between parallel edges, means for perforating or slitting said second thermoplastic film, and if necessary adjusting the width of the second web to be smaller than the width of the first web, means for overlaying the second thermoplastic film web onto the first thermoplastic film web between the parallel edges of the first film web, means for attaching the second thermoplastic film web to the first thermoplastic film web along parallel edges of the second thermoplastic film, means for folding the films in the transverse direction and means for seal cutting the folded films to form multi-layered bags.
Further according to the present invention there is an apparatus for attaching at least two film webs comprising means for providing at least a first film web having a first web width and a second film web including multiple sheets wherein the total of all the sheets gives a second web width, having first and second widths respectively, means for overlaying the second film web onto the first film web, means for providing at least one sealing band of material capable of being heat sealable to at least a portion of both film webs and means for applying the sealing band of material along and over parallel edges of the second film web.